par Wilputte‐Steinert, Mme M.L.;Fierens, Paul Jean Charles 
Référence Bulletin des Sociétés chimiques belges, 64, 7-8, page (308-332)
Publication Publié, 1955
Référence Bulletin des Sociétés chimiques belges, 64, 7-8, page (308-332)
Publication Publié, 1955
Article révisé par les pairs
| Résumé : | The correlation of the SN1 solvolysis rates of organic halides is discussed. It is shown that the equations of Winstein and Grunwald, on the one hand, and of Swain and Dittmer, on the other hand, are both consequences of the same approximations: the free activation energy is the sum of one term independant of the solvent and an other related to the action of the solvent. the action of the solvent is expressed as the product of a parameter, depending only on the structure of the halide, by a function of the solvent properties. The unambiguous experimental verification of the Winstein‐Grunwald equation in a wide variety of solvents, can be used as a mechanistic criterium. The reciprocal is not necessarily true. Experimental data show that for the pair: t‐butyl chloride‐α‐methylallyl chloride the Winstein‐Grunwald equation is a good approximation. For the other pairs of halides, the approximation is not as good. In consequence, the quantitative scale of ionising powers Y introduced by Winstein and Grunwald is of little use, since it depends on the nature of the standard halide. The Winstein‐Grunwald equation, better expressed in the form log kAa‐log kAb/log kBa‐log kBb=mAB is only a good approximation within limited classes of halides. Some causes of deviations in respect to the linear free energy law are discussed. Copyright © 1955 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim |
